Electronic lighting drivers have become a common means for driving modern lighting sources, typically Light Emitting Diodes (LEDs). Such a driver is sometimes fed through a traditional triac based lighting dimmer, connected to an AC voltage mains source. In this case undesirable interference might occur. A common interference type appears as voltage surges on the mains line, which might adversely affect the proper operation of a lighting driver.
A method and device for protecting lighting drivers from surges is described and claimed in U.S. Pat. No. 8,284,536 to Minarczyk et al. Minarczyk et al. discloses a surge protection device in the current path between a power supply and a lighting driver comprising a serial fuse and a metal oxide varistor (MOV) connected to ground. The surge protection device detects and absorbs the excess energy of surges on the power supply.
Another problem arises, in the case of an external electronic lighting dimmer, when the driver's input capacitance charges during the external dimmer's conducting period and prevents a voltage drop from developing on the external dimmer's control circuits during the dimmer cutoff period. A method and device for mitigating this problem was suggested in our previous U.S. patent application 61/081,483, the disclosure of which is incorporated herein by reference. In this publication, a loading current is applied to load the external lighting dimmer whenever the instantaneous mains AC voltage is lower than a given threshold.
However, the protection techniques that are known in the art do not provide an appropriate solution to the problem of negative interference pulses on the power supply, which decrease the instantaneous voltage and energy transferred to a lighting driver. In a lighting system wherein the lighting driver is fed through a lighting dimmer, such interference pulses may cause the lighting dimmer to cut out and, consequently, the lighting driver to drop. Negative interference pulses may result, for example, from lighting dimmers connected on the same mains line as the interfered lighting driver.